Amir and Baba's relationship changes throughout the novel. The novel starts out with Amir doing whatever he could to win his father's attention, which includes betraying his best friend, Hassan. He betrayed Hassan for his father's full attention. He then earns it when Hassan and Ali move out and Baba and Amir move to America. Here are the examples.
1. Amir and Baba's relationship is fake. Amir is pretending to be someone he is not by pretending to enjoy the soccer games Baba always takes him to see.
2. Amir and Baba's relationship becomes real when Baba is diagnosed with cancer. Amir cares for him and stays with him until he dies. They become very close.
3. Amir and Baba are very alike. They both betrayed their best friends. Baba betrayed Ali by sleeping with his wife, and Amir betrayed Hassan by not standing up for him while getting assaulted. Then they both try to redeem themselves with doing other good deeds. Baba, running an orphanage, and Amir going back to Kabul to save Sohrab, Hassan's son.
I hope these work for you :)